1. Field of the Invention
The present invention relates to a light emission device and a display device using the light emission device as a light source.
2. Description of Related Art
A liquid crystal display (LCD), which is a flat panel display device, displays an image by varying a light transmission amount at each pixel using a dielectric anisotropy property of liquid crystal that varies in a twisting angle according to a voltage applied.
The liquid crystal display includes a liquid crystal (LC) panel assembly and a backlight unit for emitting light toward the liquid crystal panel assembly. The liquid crystal panel assembly receives light emitted from the backlight unit and selectively transmits or blocks the light using a liquid crystal layer.
The backlight unit is classified according to a light source into different types, one of which is a cold cathode fluorescent lamp (CCFL). The CCFL is a linear light source that can uniformly emit light to the liquid crystal panel assembly through an optical member such as a diffusion sheet, a diffuser plate, and/or a prism sheet.
However, in the backlight unit employing the CCFL, since the CCFL emits the light through the optical members, there may be a light loss. Considering the light loss, the intensity of the light emitted from the CCFL must be increased. Therefore, the power consumption of the backlight unit employing the CCFL increases. In addition, since the backlight unit employing the CCFL cannot be large-sized due to its structural limitation, it cannot be applied to a large-sized liquid crystal display over 30-inch.
A backlight unit employing light emitting diodes (LEDs) is also well known. The LEDs are point light sources that are combined with optical members such as a reflection sheet, a light guiding plate (LGP), a diffusion sheet, a diffuser plate, a prism sheet, and/or the like, thereby forming the backlight unit. The LED type backlight unit has fast response speed and good color reproduction. However, the LED is costly and increases an overall thickness of the liquid crystal display.
As described above, the conventional backlight units have their inherent problems. In addition, the conventional backlight units must maintain a predetermined brightness when the liquid crystal display is being driven. Therefore, it is difficult to improve the display quality to a sufficient level.